Drug interactions
Fosamprenavir + Vinblastine
Severity: Major
Fosamprenavir and Vinblastine: major interaction.
Last updated Sources: US FDA label
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Fosamprenavir, whose active metabolite amprenavir inhibits CYP3A4, may increase vinblastine concentrations. Boosted regimens with ritonavir are particularly likely to cause marked rises and increased vinca alkaloid toxicity such as neutropenia and neuropathy.
What this interaction means in plain words
Fosamprenavir and Vinblastine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Why it happens
Amprenavir inhibits CYP3A4 (and possibly P-glycoprotein), decreasing vinblastine clearance.
What to do
Prefer an antiretroviral regimen without CYP3A4 inhibition during vinblastine therapy. If combined, monitor blood counts and neurologic and GI toxicity closely and reduce the vinblastine dose as needed.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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References
Other interactions of Vinblastine
Frequently asked questions
Can I take Fosamprenavir with Vinblastine?
MediHelp rates the interaction as major. Fosamprenavir and Vinblastine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Fosamprenavir, whose active metabolite amprenavir inhibits CYP3A4, may increase vinblastine concentrations. Boosted regimens with ritonavir are particularly likely to cause marked rises and increased vinca alkaloid toxicity such as neutropenia and neuropathy.
How serious is the interaction between Fosamprenavir and Vinblastine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Prefer an antiretroviral regimen without CYP3A4 inhibition during vinblastine therapy. If combined, monitor blood counts and neurologic and GI toxicity closely and reduce the vinblastine dose as needed.
What other medicines interact with Vinblastine?
MediHelp also lists interactions of Vinblastine with, for example, Adenovirus types 4 and 7 live, Apalutamide, Atazanavir. The full list is on the Vinblastine page.
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